CNS - Lecture 4

Question 1

motor commands are generated in

Answer 1

higher brain centres
final common path: sensorimotor cortex

Question 2

signals from the sensorimotor cortex descend to the

Answer 2

brainstem and spinal cord motor neurons which innervate muscle fibres

Question 3

How are output commands formed in the sensorimotor cortex and where are they sent

Answer 3

sensory input is combined with input from other parts of the brain to form output commands to the brainstem, basal ganglia, and the cerebellum.

Question 4

where does the basal ganglia and the cerebellum send their outputs to

Answer 4

the thalamus and the brainstem

Question 5

What are the Supraspinal centres involved in generating motor commands

Answer 5

sensorimotor cortex, brainstem, cerebellum, cerebral cortex, thalamus and basal ganglia

Question 6

What are the necessary requirements for the operation of feedback control?

Answer 6

• sensory information
• mechanism of comparing sensory information to the desired state

Question 7

** see document for feedback control mechanism

Question 8

the two types of muscle receptors signal changes in muscle _______ and in muscle ________

Answer 8

• length
• force

Question 9

Sensory receptor that signal changes in muscle length is called

Answer 9

muscle spindle

Question 10

where are muscle spindles located

Answer 10

parallel with the force-producing muscle fibers inside the belly of the muscle

Question 11

what are muscle spindles composed of

Answer 11

a connective tissue capsule, intrafusal muscle fibres and stretch receptors

Question 12

sensory receptor that signal changes in muscle force are called

Answer 12

golgi tendon organs (tendon organs)

Question 13

where are tendon organs located

Answer 13

tendinous fascicles at the ends of the muscle fibers

Question 14

along with responding to muscle length changes, muscle spindle group 1A afferents also respond to

Answer 14

muscle or tendon vibration

Question 15

The muscle spindle signals the length of a ______ muscle and the tendon organ signals
the force in an _______ muscle.

Answer 15

flexor
extensor

Question 16

what are extrafusal muscle fibers and it’s function

Answer 16

main muscle fibers found outside the muscle spindle that product all the measurable force

Question 17

2 types of motor neurons that innervate muscle

Answer 17

alpha motor neurons
gamma motor neurons

Question 18

alpha motor neurons activate

Answer 18

the main muscle extrafusal fibers to contract

Question 19

Gamma motor neurons activate

Answer 19

intrafusal muscle fibers

Question 20

why are sensory afferents fired more rapidly when intrafusal muscle fibers are activated

Answer 20

when activated, it stretches the elastic non-contractile middle part of the muscle spindle where the sensory endings are located

Question 21

what is the alpha-gamma coactivation theory

Answer 21

gamma motor neurons are coactivated with alpha motorneurons to keep muscle spindle afferents firing during muscle shortening

Question 22

_______ _________ of a muscle causes Golgi tendon organ afferents to respond with
______ increases in their rate of firing

Answer 22

• passive stretching
• small

Question 23

_______ of extrafusal muscle fibers causes the Golgi tendon organs to fire much more rapidly

Answer 23

contraction

Question 24

The main role of gamma motor neurons is to

Answer 24

alter the sensitivity of muscle spindles to muscle length changes

Question 25

during the stretch reflex: how do signals from the Golgi tendon organ (GTO) travel

Answer 25

signals travel to the the spinal cord

Question 26

during the stretch reflex: what is the action of the golgi tendon organs

Answer 26

the GTO afferent from the extensor muscle activates an interneuron which inhibits the extensor motor neuron. Simultaneously it activates an interneuron which activates the antagonist flexor motor neuron

Question 27

what is the flexor withdrawal reflex

Answer 27

withdrawal of a limb from a painful input

Question 28

the function of feedback control is to

Answer 28

resist change and maintain a desired state

Question 29

T/F during muscle stretch, the spinal cord reflexes act in the opposite manner as the stretch reflex

Answer 29

true

Question 30

afferent signals from nociceptors in the foot cause reflex activation of the ________________ and reflex inhibition of the __________________

Answer 30

1. flexor motor neurons
2. extensor motor neurons
   (results in lifting of leg away form stimulus)

Question 31

Primary motor cortex is also called the

Answer 31

sensorimotor cortex

Question 32

areas of the cerebral cortex that control movements of the extremities

Answer 32

pre-motor cortex, supplementary motor cortex, primary motor cortex, somatosensory cortex and parietal lobe association areas

Question 33

primary sensory cortex is also known as

Answer 33

somatosensory cortex

Question 34

what is most represented in the human somatotopic map of the primary motor cortex

Answer 34

hands and face representations

Question 35

Neurons in the primary motor cortex can be activated by moving coil over different somatotopic representation areas to elicit movement in the body (mostly face and hands). This research tool is called

Answer 35

Transcranial magnetic stimulation (TMS)

Question 36

The corticospinal tract (CTS)/pyramidal tract functions

Answer 36

• conveys signals from the sensorimotor cortex through the brainstem to the spinal cord
• CST neurons make monosynaptic connections with spinal alpha motorneurons, whose axons in turn activate muscles
• CST crosses to the contralateral side of the nervous system at the brainstem level

Question 37

what forms the corticospinal tract

Answer 37

axons from neurons in the sensorimotor cortex

Question 38

CST neurons are only ___ neuronal synapse away from muscles

Answer 38

one

Question 39

stroke, cerebrovascular accident (CVA) or brain attack all result from damage to the

Answer 39

sensorimotor cortex

Question 40

the inability to move the limb on the contralateral side of the body is called

Answer 40

hemiplegia

Question 41

symptoms of hemiplegia

Answer 41

• weakness of extremities
• exaggerated stretch reflex
• muscle spasms
• speech deficits
• attentional deficits

Question 42

speech is controlled by most people in

Answer 42

the left side of the brain

Question 43

what are the 2 main speech areas

Answer 43

• broca’s area
• wernicke’s area

Question 44

broca’s area is responsible for:
and lesions of broca’s area result in:

Answer 44

• motor aspects of speech
• motor aphasia (slurring speech)

Question 45

Wernicke’s area is responsible for:
Lesions result in:

Answer 45

• comprehension of language, association of visual, auditory and sensory input with words
• sensory aphasia and dyslexia